AR's in most enviro's aren't all that fussy what lube they get. Depends on what you want the lube to do. For AR's it really is hard to beat any of the various CLP's. If you have to clean a lot and want to save, I tell ya MMO cleand like a son of a B! I use it on shotgun extensively and leaves a mirror finish.
I'm an armorer and with AR's I use any of the more popular CLP's with Shooters Choice the one I purchase for my dept most. End of day, it's much like SN rated oils, sure some better than others BUT if you were to use the cheapest CLP and clean it the right way every time you shoot; never an issue!